The present invention relates as indicated to gas diffusers which are particularly useful in connection with the aeration treatment of sewage whereby air is introduced adjacent the bottom of a quantity of raw sewage material in the course of preparing the sewage for disposal. This mode of treatment of sewage is well known and widely practiced. There is need to provide a simple, inexpensive and effective diffuser structure; and, to this end, there has been provided a simple structure preferably formed of readily moldable plastic sections which are dimensioned and configured for mating coaction and which when assembled define a simple cavity and a ball valve assembly. The device in its preferred embodiments comprises, then, three pieces; namely, a top member having perforations therein for passage of gas therethrough, a bottom member including a gas inlet and having openings therein larger than the perforations to permit release of solid and semisolid accretions within the cavity which may enter through the perforations. The top and bottom members are desirably molded to include a valve seat and a valve stop so dimensioned and configured that when the top and bottom members are assembled and cemented together, a ball valve interposed therebetween is confined but permitted at the same time to move between a seated and an unseated position.
Fritted glass diffusers for introduction of gases into the bottom of a confined body of liquid are, of course, well known. Bubblers ranging from simple open U-tubes to sophisticated gas diffusion apparatus are known. A three-piece diffuser embodying the present invention is unknown at the present time.